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Jádro ve Pavel Cejnar Ústav částicové a jaderné fyziky službách Matematicko-fyzikální fakulta UK Novosemetrálka Young Minds, Praha, březen 2019 J. E. Lodge, "New triumphs in age-old quest for perfect timepiece" in Popular Science Monthly, New York, Vol. 119, No. 6, Dec. 1931, p. 53 Vazbová energie jádra R ≈ 1-8·10−15 m hmotnost „hmotnostní hmotnost hmotnost 17 3 jádra neutronů protonů schodek“ ρ ≈ 2·10 kg/m m( N ,Z ) N mn Z mp ( N ,Z ) proton −27 −27 mn=1.675·10 kg mp=1.673·10 kg Z Ekvivalence hmotnosti a energie E mc2 N Vazbová energie jádra – energie, která se uvolní, když neutron se protony a neutrony přiblíží a vytvoří vázaný systém (jádro): 2 2 2 B(N ,Z ) N mnc Z mpc m(N ,Z ) c 2 ( N ,Z )c Vazbová energie jádra V roce 1935 odvodil C.von Weizsäcker pro vazbovou energii jader jednoduchou formulku, která vysvětluje B [MeV] stabilitu jader v přírodě a ukazuje, že těžká jádra A mají menší vazbovou energii než středně těžká jádra. Carl Friedrich von Weizsäcker 1912-2007 B [MeV] A von Weiszäckerova formule 2 Z 2 (N Z)2 B a A a A3 a a V S C 1 A A A3 A N Z Vazbová energie jádra V roce 1935 odvodil C.von Weizsäcker pro vazbovou energii jader jednoduchou formulku, která vysvětluje B [MeV] stabilitu jader v přírodě a ukazuje, že těžká jádra A mají menší vazbovou energii než středně těžká jádra. Carl Friedrich von Weizsäcker 1912-2007 Obyčejné Při štěpení 1 jádra 235U hoření, např. se uvolní celkem cca C+O2→CO2, 210 MeV energie uvolní na (z toho cca 180 MeV 1 vzniklou okamžitě a cca 30 MeV molekulu při následných rozpadech) asi 1-10 eV ≈108 x víc energie 1 eV =1.6·10−19 J A N Z Řetězová reakce V r.1932 navrhli John Cockroft a Ernest Walton (vynálezci prvního urychlovače částic) uvolnění energie jádra pomocí reakce s urychlenými protony 7 4 4 p 3Li 2He 2 He . Jejich návrh zkritizoval Ernest Rutherford (objevitel atomového jádra). Podle něj energie jádra nemůže být prakticky využita. John Cockroft Ernest Walton 1897–1967 Ernest Rutherford 1903-95 1871-1937 Ernest Walton a jeho generátor, Cambridge, 1932 Řetězová reakce V r.1932 navrhli John Cockroft a Ernest Walton (vynálezci prvního urychlovače částic) uvolnění energie jádra pomocí reakce s urychlenými protony 7 4 4 p 3Li 2He 2 He . Jejich návrh zkritizoval Ernest Rutherford (objevitel atomového jádra). Leo Szilard 1898-1964 Podle něj energie jádra nemůže být prakticky využita. V r.1934 koná Enrico Fermi pokusy s bombardováním uranu neutrony (částice objevená v r.1932). V témže roce podává Leo Szilard patent předjímající neutrony n vyvolanou řetězovou reakci jader. Jeho návrh byl sice nereálný, 2n ale obsahoval zárodek správné n myšlenky… 2n n Štěpení jader neutron V prosinci 1938 nachází Otto Hahn a Fritz Strassmann (v Berlíně) ve Ida Noddack vzorcích uranu ozářeného neutrony 1896-1978 lehčí jádra (baryum). Lisa Meitner a Robert Frisch (v Dánsku) to vysvětlují jako výsledek štěpení jádra uranu, ke kterému dochází v důsledku „křehkosti“ těžkých jader neutrony dané elektrickým odpuzováním protonů… Pozn.: Možnost štěpení uranu navrhla na základě Fermiho experimentů již Otto Hahn 1879-1968 v r.1934 Ida Noddack. Lise Meitner 1878-1968 Rozdělení hmotnostních čísel štěpných Aparatura, na níž Hahn a Strassmann v Ústavu císaře Wilhelma v Berlíně objevili produktů štěpení (Deutsches Museum, Mnichov) (pro různá štěpená jádra) Štěpení jader neutron Niels Bohr („otec“ kvantové fyziky a spolutvůrce jaderné fyziky) v USA Robert Frisch nechtěně iniciuje „hon“ na přímý 1904-1979 důkaz štěpení (a hájí prvenství Frische v Kodani). Štěpení uranu se stává všeobecně známým jevem... Nature, 11.2.1939 neutrony Otto Hahn 1879-1968 Lise Meitner 1878-1968 Vzniká otázka, jakou roli hrají izotopy ퟐퟑퟖ ퟐퟑퟓ ퟗퟐ푼 a ퟗퟐ퐔, které vzhledem ke štěpení vykazují značně odlišné Nature, 18.2.1939 vlastnosti Štěpení jader neutron Niels Bohr 1885-1962 John Archibald Wheeler 1911- 2008 Štěpení jader neutron !!! Niels Bohr 1885-1962 řetězová reakce! Začátek války 1938 prosinec O.Hahn + F.Strassmann a R.Frisch + L.Meitner objevují 1939 štěpení uranu neutrony, rozebíhá leden se horečné zkoumání (N.Bohr…) březen Německo obsazuje (štěpí) Českoslo- vensko a získává jeho zásoby uranu srpen A.Einstein (na popud L.Szilárda) píše dopis prezidentu USA Rooseveltovi září začátek 2. světové války Rooseveltova odpověď odpověď Rooseveltova 1939 10. 19. dopis Rooseveltovi Einsteinův 1939 8. 2. Začátek války 1938 prosinec O.Hahn + F.Strassmann a R.Frisch + L.Meitner objevují 1939 štěpení uranu neutrony, rozebíhá leden se horečné zkoumání (N.Bohr…) březen Německo obsazuje (štěpí) Českoslo- vensko a získává jeho zásoby uranu srpen A.Einstein (na popud L.Szilárda) píše dopis prezidentu USA Rooseveltovi září začátek 2. světové války prosinec Werner Heisenberg iniciuje 1940 vývoj německého jaderného reaktoru (Uranmaschine) únor květen Německo dobývá Belgii a získává zásoby uranu v belgickém Kongu Heisenbergova tajná zpráva německému úřadu pro červen Německo dobývá Norsko zbraně (Heereswaffenamt, Army Weapons Bureau) a ovládá výrobu těžké vody "O možnosti produkce technické energie štěpením uranu" 6. 12. 1939 (část I) 20. 2. 1940 (část II) Případ Heisenberg Werner Heisenberg (vynikající teoretik, spoluzaklada- tel kvantové mechaniky) navštívil v září 1941 svého přítele Nielse Bohra v Kodani. Obsah jejich setkání dodnes nebyl zcela vyjasněn, ale Bohr jej interpretoval jako důkaz loajality Heisenberga (který sám byl před válkou nacisty napadán) nacistickému Německu. To ještě více urychlilo jaderný výzkum spojenců. Nicméně role Heisenberga v německém Werner Heisenberg 1901–1976 vojenském programu byla pravděpodobně přeceňována. V Kodani s N. Bohrem 1933, 1934, 1937 Případ Heisenberg Zürich, 18.12.1944 Pokus o zabití Heisenberga při jeho návštěvě ve Švýcarsku americkým agentem Morrisem „Moe“ Bergem. Heisenberg se ale zdál být pohlcen svým výzkumem v kvantové teorii a Berg od záměru upouští... Tabule z natáčení seriálu Génius Bomba versus reaktor Bikini test, 25. 7. 1946 Jaderná bomba „Jaderná fáze“ exploze je extrémně rychlý proces ( ≈ 1 μs ) vyžadující vysoce účinný štěpný materiál – ne 238U, ale 235U! Ten se v přírodním uranu nachází s příměsí jen 0,72 %. Uran pro bombu se proto musí obohacovat! Kritická hmota čistého 235U ve sférické geometrii je asi 50 kg (s odrá- žečem neutronů méně!). Heisenberg tuto hmotu silně nadhodnotil… (b) kritické (c) vliv neutronového (a) podkritické odrážeče množství množství Bomba versus reaktor regulační tyč moderátor moderátor moderátor moderátor palivová tyč palivová tyč U štěpení U pomalý rychlé neutron neutrony štěpení zpomalování U U zpomalování aktivní zóna moderního reaktoru Jaderný reaktor Může jako palivo využívat i neobohacený uran. Podmínkou je účinné a bezztrátové zpomalování neutronů. Nejefektivnější zpomalování neutronů probíhá na lehkých jádrech jako vodík, které však nesmí neutrony pohlco- vat – kandidáti: deuterium (těžká voda, D2O) nebo čistý uhlík (grafit). Bonus: V reaktoru s přírodním uranem vzniká plutonium 239Pu, které se dá použít v bombě podobně jako 235U ! krit.hmotnost 10 kg (ve sférické geometrii, bez odrážeče) Plutonium bylo objeveno na přelomu 1940-41 na cyklotronu v Berkeley Lab. Němci možnost výroby štěpitelného jádra v reaktoru začali zvažovat od 1941. Těžká voda 1 jádro D připadá na 6400 jader H. D20 se dá získávat mnohonásobnou elektrolýzou H20. Výroba těžké vody probíhala od r.1935 v Norsku. 1940: odvoz 185 kg těžké vody do Francie Továrna na (později do GB) – Joliot-Curie. těžkou vodu Po úplném obsazení Norska Německem je v Rjukanu, 1935 Norsk Hydro terčem diverzních akcí: říjen 1942: operace Freshman – seskok 4 norských parašutistů, přistání 2 kluzáků s 32 muži, havárie, část zahynula, ostatní zajati a popraveni… únor 1943: operace Gunnerside – seskok 6 norských parašutistů, pochod 50 km na lyžích, průnik do továrny, odpálení náloží, úspěšný návrat listopad 1943: bombardování továrny únor 1944: potopení trajektu SF Hydro, převážejícího barely D2O přes jezero Tinn. Dramatizace operace v roce 1948 Uranprojekt duben–říjen 1941 K.Diebner, A.Esau, W.Gerlach, O.Hahn, W.Bothe, K.Clusius, E.Schumann, P.Harteck, W.Heisenberg, C.v.Weiszäcker ….. Berlin Leipzig Různé návrhy experimentálního „reaktoru“ pro výzkum produkce neutronů při štěpení únor 1942 únor 1942 červen 1942 Uranprojekt – Lipská nehoda Exploze „jaderného reaktoru“ 23. 6. 1942 Příčina: chemické vznícení uranu. Důsledky: zpomalení německého výzkumu, ale paradoxně i zvýšené obavy spojenců... Snímky z natáčení seriálu Génius Uranprojekt – po 1942 Berlin říjen 1942 květen 1943 Nový design: neobohacený U (kovová forma) těžká voda Haigerloch → 1945 Spojenci rozebírají reaktor Útěk Nielse Bohra V září 1943 utíká Niels Bohr z Kodaně do Švédska, odtud je v říjnu transportován do GB a dále do USA, kde se připojuje k Manhattan Project. Cesta do GB se mu málem stala osudnou… rychlý bombardér de Havilland DH.98 Mosquito Manhattan Project Od konce 1939 USA a GB zkoumaly možnost vojenského použití uranu. Na konci 1941 se úsilí sjednotilo v rámci tzv. projektu Manhattan (1942-1946) Někteří známí fyzikové: R. Oppenheimer, N. Bohr, E. Fermi, J.von Neumann, R. Feynman, E. Wigner, L. Szilard, P. Auger, F. Bloch, I. Rabi, S. Anderson, J. Chadwick, R. Glauber, J. Cockroft, E. Condon, B. Pontecorvo, S. Ulam, N. Rosen, E. Teller, E. Segré, F. Reines, R. Peierls, A. Bohr …..………………… Představy o U-bombě kolem 1942 Manhattan Project – Feynman 1941-42: v Princetonu pracuje jako dobrovolník na vojenském výzkumu (balistika, separace uranu) 1943-45: Los Alamos, pracuje na výpočtech výtežku štěpné reakce (v Betheho skupině), ve výpočetním oddělení (koordinace „human computers“, později práce s mechanickými analogovými počítači – metoda děrných štítků), 1918 – 1988 v Oak Ridge na zabezpečení manipulace s obohaceným uranem, na vývoji uranové hybridní bomby (s moderátorem, později Von Neumann Ulam opuštěno), také jako partner v diskusích Feynman s Nielsem Bohrem Manhattan Project – jaderné reaktory 2. 12. 1942 bylo v Chicagu (pod sedadly stadionu Stagg Field ) pod vedením E. Fermiho uskutečněno první řízené štěpení uranu v reaktoru Chicago Pile-1 (přírodní uran, grafitový moderátor).
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    Title of Section PROJECT Y Ethan Kolkimeier • Elizabeth Lyle • Leon Staton • Yuna Susake 1 Dedicatation This book is dedicated to Dr. Robles. 3 Title of Section Table of Contents Dedicatation . 3 Introduction . 7 Origins . 7 Nuclear Fission and Atomic Bombs . 7 Bomb Design Concepts . 9 Bomb Laboratory Concept . 10 Site Selection . 11 Organization. .13 Military . 13 Civilian . 15 Gun-type weapon design . 19 Research . .19 Development. .21 Plutonium . 23 Implosion-type Weapon Design and Fat Man . 25 Little Boy . 27 Water Boiler . .30 Super. .32 Trinity . 35 Jumbo . 35 Project Alberta . 37 Health and Safety . .40 5 Project Y Security . 41 Post-war . 42 Z Division . 43 Operation Crossroads . .43 Project Y . .45 Bibliography . 47 6 Introduction Introduction The Los Alamos Laboratory, also known as “Project Y”, was a secret laboratory established by the Manhattan Project and operated by the University of California (UC) during World War II (WWII). Its mission was to design and build the first atomic bombs. Robert Oppenheimer directed it from 1943 to 1945, succeeded by Norris Bradbury. Project Y operated in a remote part of New Mexico so that scientists could freely discuss their work while preserving security. Development initially concentrated on making a nuclear fission weapon using plutonium called “Thin Man”. In 1944, Oppenheimer reorganized the laboratory and orchestrated a successful effort on an alternative design proposed by John von Neumann: a nuclear weapon they called “Fat Man”. They developed a variant of the Thin Man design called “Little Boy”, using the isotope uranium-235. Chemists at the Los Alamos Laboratory developed methods of purifying the elements uranium and plutonium, the latter an uncommon metal when Project Y began.
  • Chapter 21: Radioactivity and Nuclear Chemistry

    Chapter 21: Radioactivity and Nuclear Chemistry

    Chapter 21: Radioactivity and Nuclear Chemistry Chem 102 Jussi Eloranta Other radioactive dating applications • 14C dating works for organic objects < ~50,000 yrs old • Age of rocks can be determined by measuring: 238 206 9 U → Pb (t1/2 = 4.5 x 10 years) This ratio is set when rock forms from magma. • Oldest rocks on Earth are ~4.0 billion years old • Oldest meteorites are ~4.5 billion years old; roughly the age of our solar system 2 Nuclear fission • Lise Meitner, Fritz Strassmann, Otto Hahn in 1939: The bombardment of uranium-235 with neutrons produces elements lighter than uranium: neutron The nucleus is broken apart by neutron! 3 Chain reaction • Initial decay produces more neutrons, so if more 235U is present, the reaction can continue • Can produce a lot of energy! • Need a minimum amount of 235U; critical mass • 235U is <1% of naturally occurring U. Needs to be refined (“enriched”). Accelerating chain reaction! 4 Critical mass ● A ‘runaway’ condition exists if The ‘demon core’ enough neutrons strike enough U-235 atoms: ● If the mass is small, neutrons escape from the surface without causing enough chain reactions (subcritical) ● If the mass is large, neutrons remain inside and cause runaway (supercritical) Pu sphere surrounded by neutron-reflective blocks ● Critical mass of U-235 is ~52 kg goes supercritical if two (17 cm diameter) additional blocks are added 5 Manhattan Project $6 ms after detonation, ,-** m wide) • Development of atomic bomb ,$*!$*+ K during WW II (Oppenheimer et al.) • Especially important: How to enrich enough uranium to produce a bomb? (Oak Ridge, TN) • Bomb assembly at Los Alamos, NM First atomic bomb test in • In 1945 US dropped atomic New Mexico (Trinity test) bombs on Hiroshima and in 1%&5 had the power of Nagasaki, Japan; end of WW II $()**0 tons of TNT 6 Nuclear power • A huge amount of energy is released from nuclear fission.
  • Outdoor Travel Ountry & SPECIAL ISSUE N for Peoplewhocare West Aboutthe LOST SANCTUARIES ATOMIC TOURISTS WALKING ITOFF Ews CONTENTS

    Outdoor Travel Ountry & SPECIAL ISSUE N for Peoplewhocare West Aboutthe LOST SANCTUARIES ATOMIC TOURISTS WALKING ITOFF Ews CONTENTS

    outdoor& travel SPECIAL ISSUE High Country ForN people whoews care about the West May 13, 2019 | $5 | Vol. 51 No. 8 | www.hcn.org No. 51 | $5 Vol. 2019 13, May ATOMIC TOURISTS LOST SANCTUARIES WALKING IT OFF CONTENTS High Country News Editor’s note EXECUTIVE DIRECTOR/PUBLISHER Paul Larmer EDITOR-IN-CHIEF Road trip detours Brian Calvert FEATURES ART DIRECTOR and epiphanies Cindy Wehling DIGITAL EDITOR Last year, I found myself driving Gretchen King 12 ASSOCIATE EDITORS from Colorado’s Western Slope Tristan Ahtone to my home in North Idaho, my The Atomic Road Trip Emily Benson car loaded down with books, Maya L. Kapoor In the Land of Enchantment, camping gear and my bike. As ASSOCIATE PHOTO EDITOR histories of violence are packaged, Luna Anna Archey road trips go, it was short but sold and consumed ASSISTANT EDITORS illuminating: I saw, firsthand, a Paige Blankenbuehler fundamental truth of that place, By LuLing Osofsky and Carl Segerstrom Anna V. Smith its desert heat and fire-scarred Key MacFarlane EDITOR AT LARGE hillsides. The first evening, as dusk settled over Betsy Marston the landscape, a sign announced that the narrow COPY EDITOR Diane Sylvain highway I’d meant to take through Utah was closed. 32 CONTRIBUTING EDITORS As I detoured up the next road, I watched the glow Graham Brewer Ruxandra Guidi of a wildfire — the cause of the closure — blossom on Whose Santuario? Michelle Nijhuis the ridge to the east like a brilliant, dreadful flower, Finding and losing The world’s only UFO McDonald’s Jodi Peterson the scent of smoke filling my car.
  • PHYS1211—Part 3; Nuclear

    PHYS1211—Part 3; Nuclear

    PHYS1211—part 3; nuclear • Chapters 13, 14, and 15 of the textbook: “Energy—Its Use and the Environment”. • Prof. Michael Ashley, Room 137, Old Main Building, [email protected], pph 9385-5465. • http://mcba11.phys.unsw.edu.au/˜mcba/PHYS1211/a.pdf The atomic hypothesis • Question: is matter indefinitely divisible? • Democritus (ca. 420 BC) proposed that all matter was composed of an indivisible component: at atom. • Aristotle: (384 BC–332 BC) matter composed of four “elements”: air, fire, water, earth. • Dalton (1766–1844) proposed that each element (lead, aluminium, hydrogen, etc) consisted of only one kind of “atom”, unique to that element. • Dalton conducted chemical experiments, John Dalton e.g., combining hydrogen & oxygen in precise ratios to produce water, which strongly supported his atom hypothesis. The electron charge-to-mass ratio Thomson’s experiment • J. J. Thomson measured the charge-to-mass ratio of the electron in 1897 using an evacuated tube. http://www.youtube.com/watch?v=IdTxGJjA4Jw • Electrons (blue) are produced by heating a filament, and are then accelerated by a voltage to the right. • Electric & magnetic fields deflect the electron beam. • From the strength of the two fields, the q/m ratio can be found. • We can do this experiment in the UNSW 2nd year laboratory. Protons and neutrons • All nuclei are composed of two particles: I protons—positively charged, with exactly the opposite charge of the electron, I neutrons—no charge • The masses of these particles are: I proton—1.0072766 amu I neutron—1.0086654 amu I electron—0.0005486 amu where an atomic mass unit (amu) is 1.66×10−27 kg.